In an existing network architecture, linear protection and ring protection are most commonly used service protection modes. Linear protection is applied to a linear network, where the linear network refers to that a network topology between two network nodes is linear. Linear protection between two network nodes generally requires that multiple transport entities exist between the two network nodes, where one transport entity (transport entity) is a working transport entity, and another transport entity is a protection transport entity. A basic principle of linear protection is that, when a working transport entity becomes faulty, a network node switches a service to a path of a protection transport entity. Linear protection includes a 1+1 protection structure and a 1:1 protection structure.
When the 1+1 protection structure is used, a service is transmitted on a working transport entity and a protection transport entity simultaneously, and a receive end performs selective receiving according to a certain rule. For example, in the case of normal working, the service is received from the working transport entity; and when it is detected that the working transport entity becomes faulty, the service is received from the protection transport entity. The 1+1 protection structure may be unidirectional or bidirectional switching. In the case of unidirectional 1+1 protection, automatic protection switching (APS) packet negotiation does not need to be performed; in the case of bidirectional 1+1 protection, APS packet negotiation needs to be performed, so as to ensure that a same transport entity is selected in both directions.
The 1:1 protection structure is bidirectional. When the 1:1 protection structure is used, a transmit end and a receive end perform APS packet negotiation to determine a working transport entity, and the transmit end and the receive end send and receive a service only through the working transport entity. The transmit end and the receive end switch the service to a protection transport entity according to APS packet negotiation only when the working transport entity becomes faulty.
A network topology in a practical application is usually more complex. As shown in FIG. 1, in the prior art, nodes A, B, C, D, E, and F in a network constitute a linear protection network between the nodes A and F. In the network topology, A and F are not directly connected. It is assumed that a transport entity (that is, a transport entity 6→7→8 in the figure) from A to F through B and D is a current active transport entity; when a link (that is, a transport entity 6) between A and B becomes faulty, theoretically, a service needs to be switched to a transport entity that is from A to F through C and E (that is, a transport entity 1→2→5 in the figure), or from A to F through C and D (that is, a transport entity 1→3→8 in the figure). The node A can detect a link fault, and therefore the service is switched to a link (that is, a transport entity 1) between A and C; however, for B, D, and F, links between them are normal, and therefore a fault cannot be detected in corresponding fault detection, so that these nodes do not perform corresponding switching. Therefore, corresponding protection switching cannot be completed, and service protection cannot be implemented.